The invention relates to a clamping device between a tool shank and a machine tool. The invention relates in particular to a clamping device for cutting tools with an internal coolant supply.
The cutting principally of metals on machine tools (drills, millers, lathes) is carried out using, inter alia, cutting tools which feed the coolant directly to the cutting edge through a bore in the tool shank in order to lengthen the service life of the tool and improve its cutting capacity.
Such cutting tools usually have a round shank which is clamped in the tool holder by means of a suitable collet chuck or clamping sleeve, provided with slots for flexibility, and is thus secured against twisting. As these cutting tools with an internal coolant supply can easily be made to rotate at speeds of 40,000 rpm, enhanced cooling of the operation is essential. To improve the cooling, the pressure at which the coolant is injected is therefore increased to as much as 50 bar or more. Now, if a tool with an internal coolant supply is connected to the machine tool by means of a collet chuck or clamping sleeve, a large part of the cooling fluid is lost through the slots in the unsealed collet chuck or clamping sleeve.
To prevent this, the slots in the collet chuck or clamping sleeve have hitherto been filled with an elastic compound such as rubber, although the chucking capacity was then lost, or the tensioning nut was sealed by means of a washer, a solid sealing ring or a packing, or rubber pegs were inserted in specially made bores in the slots in the collet chuck or clamping sleeve. The disadvantages of these variants are that for every shaft or tool shank diameter there must be a washer of corresponding diameter or a packing available, and that the sealing rings or rubber pegs are no longer certain to form a seal at today's high cooling fluid pressures and are attacked by the various coolants. The greatest disadvantage of these variants, however, is that a collet chuck or clamping sleeve which had to be sealed required additional components.
The object of the invention is therefore to provide a clamping device which forms a perfect seal against the escape of fluids from machine tools, even at high pressures of up to 150 atm, and substantially retains its flexibility, and which is effective without additional sealing components and can nevertheless be used in conventional machine tools.